The tissue formation of catecholamine-derived tetrahydroisoquinolines, cyclic derivatives which could arise from acetaldehyde condensation with the neuro hormones, is being investigated in ethanol-intoxicated animals by selective gas chromatographic techniques. Evidence indicates that the isoquinoline derivatives are produced in nanogram/gram amounts when acetaldehyde metabolism is inhibited. The cyclic derivatives are being investigated for their effects on brain enzyme systems, and related tetrahydroisoquinolines are being synthesized. Other effects of ethanol and acetaldehyde on endogenous catechol levels and turnover rates are under study.